Known assemblies comprise an arm mounted to oscillate on a fixed structure that is secured to the chassis of the vehicle, said arm also being fitted with a wheel axle (or stub axle), or with a track wheel when the vehicle is a tracked vehicle such as a tank, said axle being offset relative to the oscillation axis of the arm and being situated beneath it.
In the text below, reference is made to a suspension assembly for a tracked vehicle, however the invention is naturally not limited to that particular application.
Modern tanks include a series of track wheels on either side, generally five or six of them, which support the total static load, and each of which is mounted on a respective oscillating arm. By way of example, the suspended mass per track wheel is of the order of four (metric) tonnes, such that the suspension elements need to be adapted accordingly.
The suspension elements are required not only to support the mass of the vehicle, but also to minimize effects due to movements of the body and effects due to the ground, in particular when going over obstacles at high speed.
More and more use is being made of systems that are integrated within the oscillating arm so as to achieve optimum compactness and protection, with such systems appearing to be more attractive than suspensions having transverse torsion bars, which are bulky and difficult to adjust, without mentioning the drawbacks inherent to passing through the structure.
Suspension assemblies are already known that comprise a housing receiving a shock absorber comprising interleaved friction disks and a single-chamber oleo-pneumatic spring. The shock absorber includes members enabling hydraulic compression to be exerted on the interleaved disks to implement the shock absorbing function (e.g. a cam secured to the housing of the oscillating arm, with a control finger bearing thereagainst that co-operates with the hydraulic braking system).
Such systems are advantageous insofar as the spring and shock absorbing functions are uncoupled from each other, thereby making the suspension less sensitive to temperature variation, however such systems are complex in structure because of the way in which the hydraulic compression members associated with the interleaved friction disks are organized, and consequently because of the sealing required for the corresponding portion of the suspension assembly. In addition, control of the moving finger may suffer from weaknesses under difficult conditions of use.
An object of the invention is to provide an oscillating arm suspension assembly whose structure is both simple and reliable, enabling it to be implemented in highly compact manner that is compatible with a minimum amount of space available therefor (thus making it possible to take little space from the structure of the vehicle).
Another object of the invention is to provide a suspension assembly which suffers little from temperature fluctuations, be they internal or external, and which is as independent as possible therefrom so as to have as small an effect as possible on the vehicle's ground clearance.
Another object of the invention is to provide a suspension assembly making it possible simultaneously to have good dynamic stability for the vehicle and to pass over obstacles in satisfactory manner at high speed.